Tag Archives: electronics

If you have a USB adapter and would like to use it when working with Arduino or Raspberry Pi you may wonder if it is safe to use with a 3v3 system. Purchasing these on eBay can be cheaper than buying from someplace like Adafruit but the listings often have no documentation on if the chip can be used with 3.3v devices. You can measure some of the pins to make your own determination. The unit I was working with several pins labeled: I measured voltage between the GND pin and the TX pin which gave around 1.8 – 2.5V without any data being transmitted. When I sent data to the device the voltages went intermittently to around 3.3 volts or maybe 3.4 volts. But I wanted to make sure that the chip was actually setup for 3.3v and so I found the datasheet for the PL-2303HX Make sure to get the correct datasheet for the chip you have – some of the chips are slightly different, like the HXD version. On page 11 of that datasheet it showed the pinout diagram – notice the small circle indicating “pin 1” which should correspond to the small dot on the actual chip: Pin 4 is labeled VDD_325 and the note says: RS232 VDD. The power pin for the serial port signals. When the serial port is 3.3V, this should be 3.3V. When the serial port is 2.5V, this should be 2.5V. The range can be from 1.8V~3.3V. Use this information at … Continue reading →

If you’ve installed Debian Squeeze on the PogoPlug you’ll notice there is no longer an /sys/module/xce/sections/ or /dev/xce path for you to echo commands to. However, you can still control the LEDs by using the sys -> devices -> platform -> LEDS / GPIO How to disable the LEDs echo 0 > /sys/devices/platform/leds-gpio/leds/status:red:fault/brightness echo 0 > /sys/devices/platform/leds-gpio/leds/status:green:health/brightness How to make the LED green echo 0 > /sys/devices/platform/leds-gpio/leds/status:red:fault/brightness echo 1 > /sys/devices/platform/leds-gpio/leds/status:green:health/brightness How to make the LED red echo 1 > /sys/devices/platform/leds-gpio/leds/status:red:fault/brightness echo 0 > /sys/devices/platform/leds-gpio/leds/status:green:health/brightness How to make the LED orange / yellow echo 1 > /sys/devices/platform/leds-gpio/leds/status:red:fault/brightness echo 1 > /sys/devices/platform/leds-gpio/leds/status:green:health/brightness You can also try using values 1-255 to control the brightness but I didn’t see much difference between different numbers. ymmv. Also, if you wish to read the status of the LEDs you can do so by using something like cat with these paths: cat /sys/devices/platform/leds-gpio/leds/status:red:fault/brightness A value of 0 indicates the LED is off. Most likely if you are running Debian there will be no events that turn the LEDs on – but in case you have issues you can disable system events from triggering the LEDS you also need to change the ‘triggers’ – first check out the existing ones: cat /sys/devices/platform/leds-gpio/leds/status:green:health/trigger This results in: [none] nand-disk timer oneshot ide-disk1 ide-disk2 heartbeat gpio default-on mmc0 And for the red led use: cat /sys/devices/platform/leds-gpio/leds/status:red:fault/trigger Which should result in: [none] nand-disk timer oneshot ide-disk1 ide-disk2 heartbeat gpio default-on mmc0 Next, to disable the events from triggering the LEDs run: … Continue reading →

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